Topical Fluoridation Procedures: Clinically practicable methods for incorporating increased amounts of flouride into dental enamel in the form of fluroapatite will be investigated. The basic process involves partial conversion of enamel mineral into CaHPO4.2H2O by an acid-calcium phosphate treatment. The latter is then allowed to react with F- to form fluorapatite. Laboratory studies will be used to optimize the procedures; studies with rats will be used to test the effectiveness of uptake and caries prevention; clinical studies will be carried out to measure fluoride uptake; and pilot clinical studies will be carried out to measure effectiveness in preventing caries. Caries Mechanism Studies: Laboratory scale diffusion cells will be used as models of the caries lesion. Factors such as permselectivity of the tooth surface, fluoride, strong and weak acids, and chemical potentials of components will be among the variables to be tested. Modifiers of the ionic charge on tooth surfaces will be sought through membrane potential measurements, and their effectiveness will be tested in artificial caries and animal studies. The formation of octacalcium phosphate as a precursor to enamel mineral during tooth growth and the effects of fluoride on its presence will be tested in an animal model. Etching Procedures: A procedure for etching enamel to improve bonding to resins is to be investigated. Two other objectives are to reduce loss of enamel and to permit fluoridation without loss of bond strength.